diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 0d94bfb5..597b34c8 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -4,13 +4,7 @@ require 'active_model/serializer/collection_serializer'
 require 'active_model/serializer/array_serializer'
 require 'active_model/serializer/error_serializer'
 require 'active_model/serializer/errors_serializer'
-require 'active_model/serializer/concerns/associations'
-require 'active_model/serializer/concerns/attributes'
 require 'active_model/serializer/concerns/caching'
-require 'active_model/serializer/concerns/configuration'
-require 'active_model/serializer/concerns/links'
-require 'active_model/serializer/concerns/meta'
-require 'active_model/serializer/concerns/type'
 require 'active_model/serializer/fieldset'
 require 'active_model/serializer/lint'
 
@@ -23,13 +17,16 @@ module ActiveModel
     extend ActiveSupport::Autoload
     autoload :Adapter
     autoload :Null
-    include Configuration
-    include Associations
-    include Attributes
+    autoload :Attribute
+    autoload :Association
+    autoload :Reflection
+    autoload :SingularReflection
+    autoload :CollectionReflection
+    autoload :BelongsToReflection
+    autoload :HasOneReflection
+    autoload :HasManyReflection
+    include ActiveSupport::Configurable
     include Caching
-    include Links
-    include Meta
-    include Type
 
     # @param resource [ActiveRecord::Base, ActiveModelSerializers::Model]
     # @return [ActiveModel::Serializer]
@@ -111,6 +108,200 @@ module ActiveModel
       @serialization_adapter_instance ||= ActiveModelSerializers::Adapter::Attributes
     end
 
+    # Configuration options may also be set in
+    # Serializers and Adapters
+    config.collection_serializer = ActiveModel::Serializer::CollectionSerializer
+    config.serializer_lookup_enabled = true
+
+    # @deprecated Use {#config.collection_serializer=} instead of this. Is
+    #   compatibilty layer for ArraySerializer.
+    def config.array_serializer=(collection_serializer)
+      self.collection_serializer = collection_serializer
+    end
+
+    # @deprecated Use {#config.collection_serializer} instead of this. Is
+    #   compatibilty layer for ArraySerializer.
+    def config.array_serializer
+      collection_serializer
+    end
+
+    config.default_includes = '*'
+    config.adapter = :attributes
+    config.key_transform = nil
+    config.jsonapi_pagination_links_enabled = true
+    config.jsonapi_resource_type = :plural
+    config.jsonapi_namespace_separator = '-'.freeze
+    config.jsonapi_version = '1.0'
+    config.jsonapi_toplevel_meta = {}
+    # Make JSON API top-level jsonapi member opt-in
+    # ref: http://jsonapi.org/format/#document-top-level
+    config.jsonapi_include_toplevel_object = false
+    config.include_data_default = true
+
+    # For configuring how serializers are found.
+    # This should be an array of procs.
+    #
+    # The priority of the output is that the first item
+    # in the evaluated result array will take precedence
+    # over other possible serializer paths.
+    #
+    # i.e.: First match wins.
+    #
+    # @example output
+    # => [
+    #   "CustomNamespace::ResourceSerializer",
+    #   "ParentSerializer::ResourceSerializer",
+    #   "ResourceNamespace::ResourceSerializer" ,
+    #   "ResourceSerializer"]
+    #
+    # If CustomNamespace::ResourceSerializer exists, it will be used
+    # for serialization
+    config.serializer_lookup_chain = ActiveModelSerializers::LookupChain::DEFAULT.dup
+
+    config.schema_path = 'test/support/schemas'
+
+    with_options instance_writer: false, instance_reader: false do |serializer|
+      serializer.class_attribute :_attributes_data # @api private
+      self._attributes_data ||= {}
+    end
+    with_options instance_writer: false, instance_reader: true do |serializer|
+      serializer.class_attribute :_reflections
+      self._reflections ||= {}
+      serializer.class_attribute :_links # @api private
+      self._links ||= {}
+      serializer.class_attribute :_meta # @api private
+      serializer.class_attribute :_type # @api private
+    end
+
+    def self.inherited(base)
+      super
+      base._attributes_data = _attributes_data.dup
+      base._reflections = _reflections.dup
+      base._links = _links.dup
+    end
+
+    # keys of attributes
+    # @see Serializer::attribute
+    def self._attributes
+      _attributes_data.keys
+    end
+
+    # @example
+    #   class AdminAuthorSerializer < ActiveModel::Serializer
+    #     attributes :id, :name, :recent_edits
+    def self.attributes(*attrs)
+      attrs = attrs.first if attrs.first.class == Array
+
+      attrs.each do |attr|
+        attribute(attr)
+      end
+    end
+
+    # @example
+    #   class AdminAuthorSerializer < ActiveModel::Serializer
+    #     attributes :id, :recent_edits
+    #     attribute :name, key: :title
+    #
+    #     attribute :full_name do
+    #       "#{object.first_name} #{object.last_name}"
+    #     end
+    #
+    #     def recent_edits
+    #       object.edits.last(5)
+    #     end
+    def self.attribute(attr, options = {}, &block)
+      key = options.fetch(:key, attr)
+      _attributes_data[key] = Attribute.new(attr, options, block)
+    end
+
+    # @api private
+    # maps attribute value to explicit key name
+    # @see Serializer::attribute
+    # @see ActiveModel::Serializer::Caching#fragmented_attributes
+    def self._attributes_keys
+      _attributes_data
+        .each_with_object({}) do |(key, attr), hash|
+        next if key == attr.name
+        hash[attr.name] = { key: key }
+      end
+    end
+
+    # @param [Symbol] name of the association
+    # @param [Hash<Symbol => any>] options for the reflection
+    # @return [void]
+    #
+    # @example
+    #  has_many :comments, serializer: CommentSummarySerializer
+    #
+    def self.has_many(name, options = {}, &block) # rubocop:disable Style/PredicateName
+      associate(HasManyReflection.new(name, options, block))
+    end
+
+    # @param [Symbol] name of the association
+    # @param [Hash<Symbol => any>] options for the reflection
+    # @return [void]
+    #
+    # @example
+    #  belongs_to :author, serializer: AuthorSerializer
+    #
+    def self.belongs_to(name, options = {}, &block)
+      associate(BelongsToReflection.new(name, options, block))
+    end
+
+    # @param [Symbol] name of the association
+    # @param [Hash<Symbol => any>] options for the reflection
+    # @return [void]
+    #
+    # @example
+    #  has_one :author, serializer: AuthorSerializer
+    #
+    def self.has_one(name, options = {}, &block) # rubocop:disable Style/PredicateName
+      associate(HasOneReflection.new(name, options, block))
+    end
+
+    # Add reflection and define {name} accessor.
+    # @param [ActiveModel::Serializer::Reflection] reflection
+    # @return [void]
+    #
+    # @api private
+    def self.associate(reflection)
+      key = reflection.options[:key] || reflection.name
+      self._reflections[key] = reflection
+    end
+    private_class_method :associate
+
+    # Define a link on a serializer.
+    # @example
+    #   link(:self) { resource_url(object) }
+    # @example
+    #   link(:self) { "http://example.com/resource/#{object.id}" }
+    # @example
+    #   link :resource, "http://example.com/resource"
+    #
+    def self.link(name, value = nil, &block)
+      _links[name] = block || value
+    end
+
+    # Set the JSON API meta attribute of a serializer.
+    # @example
+    #   class AdminAuthorSerializer < ActiveModel::Serializer
+    #     meta { stuff: 'value' }
+    # @example
+    #     meta do
+    #       { comment_count: object.comments.count }
+    #     end
+    def self.meta(value = nil, &block)
+      self._meta = block || value
+    end
+
+    # Set the JSON API type of a serializer.
+    # @example
+    #   class AdminAuthorSerializer < ActiveModel::Serializer
+    #     type 'authors'
+    def self.type(type)
+      self._type = type && type.to_s
+    end
+
     attr_accessor :object, :root, :scope
 
     # `scope_name` is set as :current_user by default in the controller.
@@ -131,6 +322,36 @@ module ActiveModel
       true
     end
 
+    # Return the +attributes+ of +object+ as presented
+    # by the serializer.
+    def attributes(requested_attrs = nil, reload = false)
+      @attributes = nil if reload
+      @attributes ||= self.class._attributes_data.each_with_object({}) do |(key, attr), hash|
+        next if attr.excluded?(self)
+        next unless requested_attrs.nil? || requested_attrs.include?(key)
+        hash[key] = attr.value(self)
+      end
+    end
+
+    # @param [JSONAPI::IncludeDirective] include_directive (defaults to the
+    #   +default_include_directive+ config value when not provided)
+    # @return [Enumerator<Association>]
+    #
+    def associations(include_directive = ActiveModelSerializers.default_include_directive, include_slice = nil)
+      include_slice ||= include_directive
+      return unless object
+
+      Enumerator.new do |y|
+        self.class._reflections.values.each do |reflection|
+          next if reflection.excluded?(self)
+          key = reflection.options.fetch(:key, reflection.name)
+          next unless include_directive.key?(key)
+
+          y.yield reflection.build_association(self, instance_options, include_slice)
+        end
+      end
+    end
+
     # @return [Hash] containing the attributes and first level
     # associations, similar to how ActiveModel::Serializers::JSON is used
     # in ActiveRecord::Base.
diff --git a/lib/active_model/serializer/concerns/associations.rb b/lib/active_model/serializer/concerns/associations.rb
deleted file mode 100644
index ce0ea21f..00000000
--- a/lib/active_model/serializer/concerns/associations.rb
+++ /dev/null
@@ -1,102 +0,0 @@
-module ActiveModel
-  class Serializer
-    # Defines an association in the object should be rendered.
-    #
-    # The serializer object should implement the association name
-    # as a method which should return an array when invoked. If a method
-    # with the association name does not exist, the association name is
-    # dispatched to the serialized object.
-    #
-    module Associations
-      extend ActiveSupport::Concern
-
-      included do
-        with_options instance_writer: false, instance_reader: true do |serializer|
-          serializer.class_attribute :_reflections
-          self._reflections ||= {}
-        end
-
-        extend ActiveSupport::Autoload
-        autoload :Association
-        autoload :Reflection
-        autoload :SingularReflection
-        autoload :CollectionReflection
-        autoload :BelongsToReflection
-        autoload :HasOneReflection
-        autoload :HasManyReflection
-      end
-
-      module ClassMethods
-        def inherited(base)
-          super
-          base._reflections = _reflections.dup
-        end
-
-        # @param [Symbol] name of the association
-        # @param [Hash<Symbol => any>] options for the reflection
-        # @return [void]
-        #
-        # @example
-        #  has_many :comments, serializer: CommentSummarySerializer
-        #
-        def has_many(name, options = {}, &block) # rubocop:disable Style/PredicateName
-          associate(HasManyReflection.new(name, options, block))
-        end
-
-        # @param [Symbol] name of the association
-        # @param [Hash<Symbol => any>] options for the reflection
-        # @return [void]
-        #
-        # @example
-        #  belongs_to :author, serializer: AuthorSerializer
-        #
-        def belongs_to(name, options = {}, &block)
-          associate(BelongsToReflection.new(name, options, block))
-        end
-
-        # @param [Symbol] name of the association
-        # @param [Hash<Symbol => any>] options for the reflection
-        # @return [void]
-        #
-        # @example
-        #  has_one :author, serializer: AuthorSerializer
-        #
-        def has_one(name, options = {}, &block) # rubocop:disable Style/PredicateName
-          associate(HasOneReflection.new(name, options, block))
-        end
-
-        private
-
-        # Add reflection and define {name} accessor.
-        # @param [ActiveModel::Serializer::Reflection] reflection
-        # @return [void]
-        #
-        # @api private
-        #
-        def associate(reflection)
-          key = reflection.options[:key] || reflection.name
-          self._reflections[key] = reflection
-        end
-      end
-
-      # @param [JSONAPI::IncludeDirective] include_directive (defaults to the
-      #   +default_include_directive+ config value when not provided)
-      # @return [Enumerator<Association>]
-      #
-      def associations(include_directive = ActiveModelSerializers.default_include_directive, include_slice = nil)
-        include_slice ||= include_directive
-        return unless object
-
-        Enumerator.new do |y|
-          self.class._reflections.values.each do |reflection|
-            next if reflection.excluded?(self)
-            key = reflection.options.fetch(:key, reflection.name)
-            next unless include_directive.key?(key)
-
-            y.yield reflection.build_association(self, instance_options, include_slice)
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/concerns/attributes.rb b/lib/active_model/serializer/concerns/attributes.rb
deleted file mode 100644
index 6ee2732f..00000000
--- a/lib/active_model/serializer/concerns/attributes.rb
+++ /dev/null
@@ -1,82 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Attributes
-      extend ActiveSupport::Concern
-
-      included do
-        with_options instance_writer: false, instance_reader: false do |serializer|
-          serializer.class_attribute :_attributes_data # @api private
-          self._attributes_data ||= {}
-        end
-
-        extend ActiveSupport::Autoload
-        autoload :Attribute
-
-        # Return the +attributes+ of +object+ as presented
-        # by the serializer.
-        def attributes(requested_attrs = nil, reload = false)
-          @attributes = nil if reload
-          @attributes ||= self.class._attributes_data.each_with_object({}) do |(key, attr), hash|
-            next if attr.excluded?(self)
-            next unless requested_attrs.nil? || requested_attrs.include?(key)
-            hash[key] = attr.value(self)
-          end
-        end
-      end
-
-      module ClassMethods
-        def inherited(base)
-          super
-          base._attributes_data = _attributes_data.dup
-        end
-
-        # @example
-        #   class AdminAuthorSerializer < ActiveModel::Serializer
-        #     attributes :id, :name, :recent_edits
-        def attributes(*attrs)
-          attrs = attrs.first if attrs.first.class == Array
-
-          attrs.each do |attr|
-            attribute(attr)
-          end
-        end
-
-        # @example
-        #   class AdminAuthorSerializer < ActiveModel::Serializer
-        #     attributes :id, :recent_edits
-        #     attribute :name, key: :title
-        #
-        #     attribute :full_name do
-        #       "#{object.first_name} #{object.last_name}"
-        #     end
-        #
-        #     def recent_edits
-        #       object.edits.last(5)
-        #     end
-        def attribute(attr, options = {}, &block)
-          key = options.fetch(:key, attr)
-          _attributes_data[key] = Attribute.new(attr, options, block)
-        end
-
-        # @api private
-        # keys of attributes
-        # @see Serializer::attribute
-        def _attributes
-          _attributes_data.keys
-        end
-
-        # @api private
-        # maps attribute value to explicit key name
-        # @see Serializer::attribute
-        # @see FragmentCache#fragment_serializer
-        def _attributes_keys
-          _attributes_data
-            .each_with_object({}) do |(key, attr), hash|
-              next if key == attr.name
-              hash[attr.name] = { key: key }
-            end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/concerns/caching.rb b/lib/active_model/serializer/concerns/caching.rb
index 4809f4cb..c8340787 100644
--- a/lib/active_model/serializer/concerns/caching.rb
+++ b/lib/active_model/serializer/concerns/caching.rb
@@ -40,9 +40,9 @@ module ActiveModel
 
       module ClassMethods
         def inherited(base)
-          super
           caller_line = caller[1]
           base._cache_digest_file_path = caller_line
+          super
         end
 
         def _cache_digest
diff --git a/lib/active_model/serializer/concerns/configuration.rb b/lib/active_model/serializer/concerns/configuration.rb
deleted file mode 100644
index d6d3c610..00000000
--- a/lib/active_model/serializer/concerns/configuration.rb
+++ /dev/null
@@ -1,59 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Configuration
-      include ActiveSupport::Configurable
-      extend ActiveSupport::Concern
-
-      # Configuration options may also be set in
-      # Serializers and Adapters
-      included do |base|
-        config = base.config
-        config.collection_serializer = ActiveModel::Serializer::CollectionSerializer
-        config.serializer_lookup_enabled = true
-
-        def config.array_serializer=(collection_serializer)
-          self.collection_serializer = collection_serializer
-        end
-
-        def config.array_serializer
-          collection_serializer
-        end
-
-        config.default_includes = '*'
-        config.adapter = :attributes
-        config.key_transform = nil
-        config.jsonapi_pagination_links_enabled = true
-        config.jsonapi_resource_type = :plural
-        config.jsonapi_namespace_separator = '-'.freeze
-        config.jsonapi_version = '1.0'
-        config.jsonapi_toplevel_meta = {}
-        # Make JSON API top-level jsonapi member opt-in
-        # ref: http://jsonapi.org/format/#document-top-level
-        config.jsonapi_include_toplevel_object = false
-        config.include_data_default = true
-
-        # For configuring how serializers are found.
-        # This should be an array of procs.
-        #
-        # The priority of the output is that the first item
-        # in the evaluated result array will take precedence
-        # over other possible serializer paths.
-        #
-        # i.e.: First match wins.
-        #
-        # @example output
-        # => [
-        #   "CustomNamespace::ResourceSerializer",
-        #   "ParentSerializer::ResourceSerializer",
-        #   "ResourceNamespace::ResourceSerializer" ,
-        #   "ResourceSerializer"]
-        #
-        # If CustomNamespace::ResourceSerializer exists, it will be used
-        # for serialization
-        config.serializer_lookup_chain = ActiveModelSerializers::LookupChain::DEFAULT.dup
-
-        config.schema_path = 'test/support/schemas'
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/concerns/links.rb b/lib/active_model/serializer/concerns/links.rb
deleted file mode 100644
index 1322adb0..00000000
--- a/lib/active_model/serializer/concerns/links.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Links
-      extend ActiveSupport::Concern
-
-      included do
-        with_options instance_writer: false, instance_reader: true do |serializer|
-          serializer.class_attribute :_links # @api private
-          self._links ||= {}
-        end
-
-        extend ActiveSupport::Autoload
-      end
-
-      module ClassMethods
-        def inherited(base)
-          super
-          base._links = _links.dup
-        end
-
-        # Define a link on a serializer.
-        # @example
-        #   link(:self) { resource_url(object) }
-        # @example
-        #   link(:self) { "http://example.com/resource/#{object.id}" }
-        # @example
-        #   link :resource, "http://example.com/resource"
-        #
-        def link(name, value = nil, &block)
-          _links[name] = block || value
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/concerns/meta.rb b/lib/active_model/serializer/concerns/meta.rb
deleted file mode 100644
index 5160585e..00000000
--- a/lib/active_model/serializer/concerns/meta.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Meta
-      extend ActiveSupport::Concern
-
-      included do
-        with_options instance_writer: false, instance_reader: true do |serializer|
-          serializer.class_attribute :_meta # @api private
-        end
-
-        extend ActiveSupport::Autoload
-      end
-
-      module ClassMethods
-        # Set the JSON API meta attribute of a serializer.
-        # @example
-        #   class AdminAuthorSerializer < ActiveModel::Serializer
-        #     meta { stuff: 'value' }
-        # @example
-        #     meta do
-        #       { comment_count: object.comments.count }
-        #     end
-        def meta(value = nil, &block)
-          self._meta = block || value
-        end
-      end
-    end
-  end
-end
diff --git a/lib/active_model/serializer/concerns/type.rb b/lib/active_model/serializer/concerns/type.rb
deleted file mode 100644
index c37c9af8..00000000
--- a/lib/active_model/serializer/concerns/type.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-module ActiveModel
-  class Serializer
-    module Type
-      extend ActiveSupport::Concern
-
-      included do
-        with_options instance_writer: false, instance_reader: true do |serializer|
-          serializer.class_attribute :_type # @api private
-        end
-
-        extend ActiveSupport::Autoload
-      end
-
-      module ClassMethods
-        # Set the JSON API type of a serializer.
-        # @example
-        #   class AdminAuthorSerializer < ActiveModel::Serializer
-        #     type 'authors'
-        def type(type)
-          self._type = type && type.to_s
-        end
-      end
-    end
-  end
-end